The present invention relates to a system for measuring a tilt of an image plane, which is formed by a lens, with respect to a predetermined plane.
A lens system used in an optical instrument such as a camera, binoculars, etc., has a casing which houses many lenses. In order to produce a well focused image, the lenses must be aligned accurately within the casing. If even one of the lenses is misaligned, the resulting image plane may be tilted. If the image plane is tilted, the central area of the image would be focused, but the peripheral area of the image would be out-of-focus. Thus, the lens must be carefully assembled.
Even if the assembly is carefully monitored, a misalignment of a lens could result in the image plane being inclined with respect to the desired image plane.
On the other hand, even if a carefully assembled lens is employed in a camera, the film plane of the camera could be inclined with respect to an image plane formed by the lens.